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International symposium on coastal ecosystem change in Asia:
hypoxia, eutrophication, and nutrient conditions
Nov 14-15, 2019
Ehime University, JAPAN
International symposium on coastal ecosystem change in Asia: hypoxia,
eutrophication, and nutrient conditions
Date: November 14-15, 2019
Place: Media Hall, Ehime University, Matsuyama, Japan
(1st floor of Center for Information Technology, Ehime University)
Organizing Committee: Xinyu GUO, Akihiko MORIMOTO, Michinobu KUWAE, Naoki
YOSHIE (Center for Marine Environmental Studies, Ehime University)
Purpose:
With increasing of nutrient load into coastal water, some environmental issues have
been reported to occur in many bays and shelf seas in Asia. For example, hypoxia water
has been observed in the Bohai Sea, East China Sea, Thailand Bay, and Jakarta Bay in
recent 10 years. On the other hand, the hypoxia water has been reported in many bays and
inland seas in Japan for more than 30 years. The reduction of nutrient load into coastal
water in Japan has been continued for many years but the hypoxia water is still observed
now. Apparently, the occurrence of hypoxia water is not a simple problem related only to
nutrients load into the coastal water. The eutrophication and nutrient condition outside the
coastal water should also affect the occurrence of hypoxia water. This symposium will
provide an opportunity to summarize our understanding on the occurrence of hypoxia
water and some related issues in the coastal water in Asia.
Schedule:
November 14
9:00-9:30 Registration
9:30-9:45 Opening remark (Prof. Shinsuke TANABE, Director of Center for Marine
Environmental Studies, Ehime University, Japan)
Chair of Session: Akihiko MORIMOTO
9:45-10:15
1
Chen-Tung Arthur CHEN (National Sun Yat-sen University, Taiwan): Kuroshio and
Hypoxia in the East and South China Seas
10:15-10:45
Di TIAN (Second Institute of Oceanography, China): Impact of dissolved oxygen and
nutrients from Kuroshio on the hypoxia off the Changjiang Estuary
10:45-11:15
Feng ZHOU (Second Institute of Oceanography, China): The connection and
disconnection of phytoplankton production and subsurface hypoxia: hints from the
physically complex dynamic system off the Changjiang Estuary
11:15-11:45
Xinyu GUO (Ehime University, Japan): A method for tracing nutrients from different
origins in a low-trophic ecosystem model and evaluating their contribution to primary
production in a shelf sea
11:45-12:00 Group photo
12:00-14:00 Lunch and poster session
Chair of Session: Feng ZHOU
14:00-14:30
Xiaohui LIU (Second Institute of Oceanography, China): On the vorticity balance of the
on-shelf Kuroshio intrusion northeast of Taiwan
14:30-15:00
Ting-Hsuan HUANG (National Sun Yat-sen University, Taiwan): The Taiwan Strait
resembles a quasi-cul-de-sac in late NE monsoon season
15:00-15:30
Goh ONITSUKA (National Research Institute of Fisheries and Environment of Inland
Sea, Japan Fisheries Research and Education Agency, Japan): Harmful algal blooms in
western Japan
2
15:30-15:45 Coffee Break
Chair of Session: Yuichi HAYAMI
15:45-16:15
Anukul BURANAPRATHEPRAT (Burapha University, Thailand): Material transport
from the river mouths to the Upper Gulf of Thailand under variations in river discharge
16:15-16:45
Akihiko MORIMOTO (Ehime University, Japan): Hypoxia in the Upper Gulf of
Thailand –Hydrographic observation and modeling-
16:45-17:15
Jianping GAN (Hong Kong University of Science and Technology, Hong Kong): On
Ocean Circulation, Ecosystem and Hypoxia along the coastal transition zone off Hong
Kong (OCEAN_HK)
18:00 Reception
November 15
Chair of Session: Muhammad ILYAS
9:00- 9:30
Ario DAMAR (Bogor Agricultural University, Indonesia): The eutrophication states and
nutrient-phytoplankton dynamics of eutrophied tropical embayment of Jakarta Bay,
Indonesia: temporal dynamics from 2001 to 2017
9:30- 10:00
Suhendar I SACHOEMAR (Agency for the Assessment and Application of Technology,
Indonesia): The environmental study to understand the hypoxia behavior in Jakarta Bay
10:00- 10:30
Endro SOEYANTO (Agency for the Assessment and Application of Technology,
Indonesia): Behavior and residence time of river waters in Jakarta Bay
3
10:30-10:45 Coffee Break
Chair of Session: Naoki YOSHIE
10:45-11:15
Haruo ANDO (Tokyo Metropolitan Research Institute for Environmental Protection,
Japan): Long-term change in the state of water pollution in Tokyo Bay: Tokyo Bay,
trend analysis, COD, nutrients and hypoxia
11:15-11:45
Satoshi AKIYAMA (Research Institute of Environmental, Agriculture and Fisheries,
Osaka Prefecture, Japan): Tempo-spatial variations of hypoxia water and nutrient
conditions, and emerging problems in Osaka Bay, Japan
11:45-12:15
Chiho SUKIGARA(Tokyo University of Marine Science and Technology): Oxygen
consumption rate in the Mikawa Bay using an optical oxygen sensor
12:15-14:00 Lunch and poster session
Chair of Session: Goh ONITSUKA
14:00-14:30
Yuichi HAYAMI (Saga University, Japan): Hypoxic water mass in Ariake Sea, Japan -
mechanisms of multi-time scale variations-
14:30-15:00
Tetsuo YANAGI (Kyushu University, Japan): Disappearance of hypoxia in Dokai Bay,
Japan
15:00-15:30
Toshiyuki TAKAO (Waterfront Vitalization and Environment Research Foundation,
Japan): Enhancing water exchange and suppressing the effects of anoxic water in an
inner bay by placement of water flow pipes through tsunami protection breakwaters
15:30-15:45 Coffee Break
4
Chair of Session: Xinyu GUO
15:45-16:15
Michinobu KUWAE (Ehime University, Japan): Decadal and centennial variability in
fish abundance in the Seto Inland Sea during the last 2900 years
16:15-16:45
Naoki YOSHIE (Ehime University, Japan): Long-term variation of nutrient
concentration in the Western Seto Inland Sea
16:45-17:15
Moriaki YASUHARA (The University of Hong Kong, Hong Kong): Human-induced
marine ecological degradation: historical ecology and the Anthropocene
17:15-17:30 Closing remark (Tetsuo YANAGI, Kyushu University, Japan)
5
Poster Session
P-01 Naho MIYAZAKI (Tokyo University of Marine Science and Technology, Japan):
A challenge on measuring photosynthetic oxygen evolution by optical
sensors in the Tokyo Bay, off Haneda
P-02 Xiaokun DING(Ocean University of China, China): The river discharge can
change the peak and its occurrence time of the Chlorophyll-a in a semi-enclosed
sea
P-03 Hao JIANG(Tianjin University of Science and Technology, China): Annual
Cycles and Budgets of Nutrients in the Yellow Sea: a model study
P-04 Jun-Yong ZHENG(Ocean University of China, China): Estimate of
environmental capacity of dissolved inorganic nitrogen in the Xiangshan Bay
P-05 Qian LENG(Ocean University of China, China): Study on the Response
Mechanism of Primary Production in the East China Sea to the Change of
Nutrient Inputs from the Yangtze River
P-06 Aobo WANG(Ocean University of China, China): A simulation of the seasonal
variation of decabromodiphenyl ether in a bay adjacent to the Yellow Sea
P-07 Xiaolu WANG (East China Normal University, China): Organic Carbon
Distribution and Budget in the Changjiang Diluted Plume based on Chemical
analysis and Numerical Model
P-08 Jiliang XUAN(Second Institute of Oceanography, China): The role of
submesoscale advections on vertical heat and nutrient transports in the Southern
East China Sea
P-09 Xiaojie YU (Ocean University of China, China): Upstream propagation of a
bottom-advected plume and its influencing factors
6
P-10 Yongjiu XU (Zhejiang Ocean University, China): Effects of climate change and
human activities on the dynamics of fisheries community and succession of
dominant species in Zhoushan archipelago Seas
November 16: Field observation
References
Center for Information Technology, Ehime University
Address: 3 Bunkyo-cho, Matsuyama 790-8577, Japan
Website: http://www.ehime-u.ac.jp
Location & Campus (English)
https://www.ehime-u.ac.jp/en_page/access/johoku-campus/
Location & Campus (Japan)
https://www.ehime-u.ac.jp/overview/access/johoku/
The poster presentation will be held in the space beside the Media Hall. The size of
poster should be smaller than 110 cm (width) x 160 cm (length).
About Matsuyama
http://www.city.matsuyama.ehime.jp/lang/en/ (English)
http://www.city.matsuyama.ehime.jp/lang/ch/ (Chinese)
http://www.city.matsuyama.ehime.jp (Japanese)
7
Title: Kuroshio and Hypoxia in the East and South China Seas
Hon Kit Lui and Chen-Tung Arthur Chen*
Department of Oceanography, National Sun Yat-sen Univ., Kaohsiung, Taiwan
Abstract:
Hypoxia off the Changjiang River mouth has grown into world's largest in size
during the past two decades. The Pearl River mouth has also started to develop
hypoxia in the past two decades. Decomposition of terrestrial organic material and
oceanic phytoplankton supported by the riverine nutrients are the major causes of
hypoxia. Here we will show that the hypoxic condition off Hong Kong is diminished
when the Kuroshio intrusion to the South China Sea intensifies, perhaps due to the
enhanced supply of oxygen by the upper Kuroshio Tropical Water. The hypoxic
condition off the Changjiang River mouth also seems to be affected by the Kuroshio
intrusion to the East China Sea.
8
Title: Impact of dissolved oxygen and nutrients from Kuroshio on the hypoxia off the
Changjiang Estuary
Di Tian1, Feng Zhou1,2, Daji Huang1,2
1. State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of
Oceanography, Ministry of Natural Resources, Hangzhou, China
2. Ocean College, Zhejiang University, Zhoushan, China
Abstract:
The Changjiang Estuary (CJE), the coastal water of East China Sea, is suffering from
frequent and series hypoxia in spring and summer. The cause for large variability of
hypoxia off the CJE has not been well understood, partly due to various nutrient sources
(adjacent river and the Kuroshio) and complex physical-biological processes involved.
What extent the oceanic sources of dissolved oxygen (DO) from the Kuroshio and the
Taiwan Strait could affect the hypoxia off the CJE is also unclear.
The Regional Ocean Modeling Systems (ROMS) coupled with Carbon, Silicate and
Nitrogen Ecosystem (CoSiNE) is used to investigate the impact of dissolved oxygen
and different nutrients from Kuroshio and Taiwan Strait on the hypoxia in the East
China Sea (ESC). The sensitivity analyses suggest that dissolved oxygen (DO)
concentration in the CJE is affected by both DO water and nutrients supply to the ECS
shelf by the Kuroshio intrusion. The effect of the Kuroshio intrusion on DO in the ECS
is even larger than Kuroshio intrusion on the nutrients. The sensitivity analyses also
suggest the hypoxia extent in Changjiang Estuary is more sensitive to the change in the
phosphate concentration than other nutrients in the Kuroshio.
9
Title: The connection and disconnection of phytoplankton production and subsurface
hypoxia: hints from the physically complex dynamic system off the Changjiang Estuary
Feng Zhou1, Fei Chai1, 2, Daji Huang1, Huijie Xue2, Mark Wells2, Chenggang Liu1, Jilan Su1
1. State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of
Oceanography, Ministry of Natural Resources, Hangzhou, China
2. School of Marine Science, University of Maine, United States of America
Abstract:
The global increase in near-shore hypoxia over the past decades has resulted from
excess anthropogenic nutrient loading of surface waters relative to the residence time
of subsurface waters. The spatial relationship between surface phytoplankton
production and subsurface hypoxic zones often is readily explained by considering the
oceanographic conditions associated with basin size, shape, or bathymetry, but that is
not the case where nutrient-enriched estuarine waters merge into complex coastal
circulation systems. We investigated the physical and biogeochemical processes that
create high-biomass phytoplankton blooms and hypoxia off the Changjiang (Yangtze)
Estuary in the East China Sea (ECS). Extensive in situ datasets were linked with a
coupled Regional Ocean Modelling Systems (ROMS) and Carbon, Silicate and
Nitrogen Ecosystem (CoSiNE) model to explain the connect and disconnect of
phytoplankton production and hypoxia. Diatoms were the major contributor of carbon
export, and even though phytoplankton concentrations generally were three times
greater above the hypoxic zones, high-biomass distributions during the summer-fall
period did not closely align with that of the hypoxic zones. A major cause for this
decoupling was the non-uniform offshore advection and detachment of segments of
water underlying the Changjiang river plume, which carried organic-rich subsurface
water northeast of the river mouth. The remineralization of this dissolved organic matter
during transit created offshore patches of hypoxia spatially and temporally independent
of the nearshore high biomass phytoplankton blooms. The absence of high
phytoplankton biomass offshore, and the 1-8 weeks time lag between the inshore
diatom production and offshore hypoxia, made it otherwise difficult to mechanistically
explain the in situ observations. The findings here highlight the value of developing
integrated physical and biogeochemical models to aid in forecasting the dynamics of
coastal hypoxia, under both contemporary and future coastal ocean conditions.
10
Title: A method for tracing nutrients from different origins in a low-trophic
ecosystem model and evaluating their contribution to primary production in a shelf
sea
Jing Zhang1, Xinyu Guo2, Liang Zhao1
1. College of Marine and Environmental Sciences, Tianjin University of Science and
Technology, Tianjin, China
2. Center for Marine Environmental Studies, Ehime University, Matsuyama, Japan
Abstract:
Nutrients (dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus
(DIP)) in the East China Sea (ECS) have four external sources, namely the Kuroshio,
Taiwan Strait, rivers, and the atmosphere. In order to evaluate the contribution of each
source of nutrients to the nutrient inventory and primary production over the ECS
shelf, a tracking technique was applied to all the state variables in a low-trophic
ecosystem model. Each source of nutrients has strong seasonal variations in the
spatial distribution that depends closely on circulation, mixing, and stratification. The
primary production supported by each source of nutrient is under the control of a
combination of nutrients, temperature, and light. As a mean state over the entire ECS
shelf, the Kuroshio contributes 72% of DIN input and 84% of DIP input, 57% of DIN
inventory and 78% of DIP inventory, 50% DIN-based primary production and 61%
DIP-based primary production and therefore is the dominant one among four sources.
However, the contributions of four external nutrients have strong spatial dependence:
the riverine nutrients and the atmospheric DIN dominate the inner shelf (0-50 m), the
nutrients from the Taiwan Strait dominate the southern part of the middle shelf (50-
100 m), and the nutrients from the Kuroshio dominate the outer shelf (100-200 m).
The production efficiencies of the nutrients from the Kuroshio are low, while those
from the atmosphere and Taiwan Strait are high. The riverine DIN is inefficient but
DIP is efficient. The nutrient limitation, light and water temperature at the location of
the nutrients determine the production efficiency of each specific sources.
11
Title :On the vorticity balance of the on-shelf Kuroshio intrusion northeast of Taiwan
Xiaohui Liu1
1. State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of
Oceanography, Ministry of Natural Resources, China
Abstract:
Two expressions of the vertical-averaged vorticity balance during the Kuroshio on-shelf
intrusion northeast of Taiwan were discussed by using a regional high-resolution numerical
model. The vorticity balance formed by depth-averaged momentum equations shows that,
although the advection of geostrophic potential vorticity is mainly balanced by the joint effect
of baroclinicity and relief (JEBAR), the ageostrophic terms contributed mostly by the
advection of relative potential vorticity is the key dynamic mechanism changing the potential
vorticity. The vorticity balance formed by depth-integrating momentum equations suggests the
variation of vertical-integrating geostrophic potential vorticity is consequence of the curl of
advection caused by the Kuroshio mainstream. The vertical motion near the shelfbreak is also
the consequence of the variation of vertical-integrating potential vorticity. The sensitivity test
by removing the advection term shows that the Kuroshio on-shelf intrusion is largely decreased
due to smaller ageostrophic effects. The vertical motion is also much weaker in the absence of
advection.
12
Title: The Taiwan Strait resembles a quasi-cul-de-sac in the NE monsoon season
Ting-Hsuan Huang, Chen-Tung Arthur Chen*
Department of Oceanography, National Sun Yat-sen University, Kaohsiung, Taiwan
Abstract:
The Taiwan Strait (TS) is the thoroughfare connecting two of the largest marginal
seas in the world, namely the East China Sea (ECS) and the South China Sea (SCS).
In summer when the SW monsoon prevails the flow is all northward thus transporting
the salty, oligotrophic SCS water towards the ECS. In winter when the NE monsoon
prevails the fresh, nutrient-rich China Coastal Current (CCC) flows southward.
However, 26 ± 26 percent of the CCC turns eastward after entering the TS and then
turns back towards the ECS. In the southern TS a mixture of the SCS water and the
Kuroshio branch water flows northward initially on the eastern part of the strait. Yet,
46 ± 34 percent of this flow turns towards the west and eventually returns to the SCS
resulting in reduced exchange between the ECS and the SCS in winter. Here we
compare the northward transport situations during the SW and NE monsoons (SW:
May-Oct.; NE: Nov.-Apr.). The northward water transport to the ECS is two times
higher during the SW monsoon (2.3±0.7 Sv) than in the NE monsoon (1.2±0.5 Sv).
However, the N transport to the ECS is only half during the SW monsoon (1.5±0.6
kmol N s-1) compared to that during the NE monsoon (2.9±1.2 kmol N s-1).
Correspondingly, the N/P increases from 6.3±2.5 (the SW monsoon) to 14.4±4.0 (the
NE monsoon) which is closer to the Redfield Ratio of 16. The northward transport has
a higher N flux and more suitable N/P for biological uptake in the NE monsoon than
in the SW monsoon. To conclude, as the ECS water has a N/P ratio higher than the
Redfield ratio and vice versa for the SCS water, mixing of the waters from these two
seas results in a N/P ratio chose to the Redfield ratio, and is more suitable for
phytoplankton to grow.
13
Title: Harmful algal blooms in western Japan
Goh Onitsuka1
1. National Research Institute of Fisheries and Environment of Inland Sea, Japan
Fisheries Research and Education Agency, Hatsukaichi, Hiroshima, Japan
Abstract:
Harmful algal blooms (HABs) have occurred mainly in the Seto Inland Sea and
around Kyushu area located in western Japan. In the Seto Inland Sea, during the period
of high economic growth from the 1960s to the 1970s, the rapid increase in HABs due
to industrialization and urbanization became social problem. In particular, the bloom of
raphidophyte genus Chattonella caused the catastrophic mass mortality of 14 million
cultured yellowtail with a value of about 7.1 billion JPY in 1972. The number of bloom
occurrences decreased in the 1970s to the 1980s possibly due to the contribution of the
reduction of the loads of nitrogen and phosphorus. However, since the 1990s, there have
been around 100 bloom events per year, and HABs with fishery damage have still
occurred. From the 1970s to the 1980s, Chattonella blooms accounted for most of the
fishery damage in the Seto Inland Sea, but since the 1990s, large-scale blooms of this
species have decreased. In contrasts, harmful blooms of dinoflagellate Karenia
mikimotoi have occurred almost every year in western Japan, and frequently caused
fishery damage in recent years. Comparing the biological characteristics of Chattonella
spp. and K. mikimotoi, these species have different physiological responses to the
environmental conditions. For instance, it has been reported that K. mikimotoi can
survive longer in a low nutrient condition. The differences in responses to environments
may have led to the change in HAB species.
14
Title: Material transport from the river mouths to the upper Gulf of Thailand
Anukul Buranapratheprat1, Arvut Munhapon1,2, Siraporn Tong-u-dom1 and
Akihiko Morimoto3
1. Department of Aquatic Science, Faculty of Science, Burapha University, Thailand
2. Institute of Marine Science, Burapha University
3. Center for Marine Environmental Studies, Ehime University, Matsuyama, Japan
Abstract:
Eutrophication-related problems in coastal areas have long been occurring in
the world including the upper Gulf of Thailand. Organic materials and nutrients from
natural and anthropogenic sources transported through rivers are the major course of
red tide and hypoxia in water column. Seasonal variations in wind, circulation and river
discharge are able modify the problems to be complex in both spatial and temporal
scales. In the upper Gulf of Thailand, severe red tide usually occurs in the northeastern
corner of the area during the southwest monsoon. We all know that large river discharge
and eastward circulation developed along the northern coast trigger eutrophication
during this time. The major sources of nutrients are from four rivers including the
Maeklong River, the Thachin River, the Chaopraya River and the Bangpakong River,
located from the west to the east, but the influences of each river in the area are still
unknown. We apply a circulation model coupled with passive tracer experiments to
investigate the influence of each river in this area. It was found that most river water
transported into the area came mainly from the Chaopraya River for 33 – 40 percent,
followed by those from the Maeklong River and the Bangpakong River in almost the
same portions for about 25 – 30 percent. The results help us understand the roles of
wind, circulation and river discharge on eutrophic condition in this area through nutrient
transport.
15
Title: Hypoxia in the Upper Gulf of Thailand –Hydrographic observation and
modeling-
Akihiko Morimoto1, Yoshishisa Mino2, Anukul Buranapratheprat3,
Atsushi Kaneda4, Siraporn Tong-U-Dom3, and Xinyu Guo1
1Center for Marine Environmental Studies, Ehime University, Japan2Institute for Space-Earth Environmental Research, Nagoya University, Japan 3Department of Aquatic Science, Faculty of Science, Burapha University, Thailand 4Facultiy of Marine Science and Technology, Fukui Prefectural University, Japan
Abstract: The Upper Gulf of Thailand (UGoT) faces to capital city of Thailand,
Bangkok. Width and length of the UGoT are approximately 100 km and the UGoT is
very shallow bay with maximum water depth of 30 m. Five rivers, Bangpakong,
Chaopraya, Thachin, Maeklong, and Phet Chaburi supply fresh water and materials
such as nutrients, organic matters into the UGoT. Although the UGoT is high
productivity coastal sea with high fish production, recently marine environment in
UGoT becomes worse due to large input of organic and inorganic matters from above
five rivers. In the present study, we conducted hydrographic observation for 1 year to
understand seasonal variation in bottom DO distribution. Hypoxia appeared in river
mouth of Chaopraya in August. The hypoxia occupied in half of total area of UGoT in
September and DO concentration was less than 1 mg/l west of river mouth of
Chaopraya; anoxic condition there. Anoxia and hypoxia occurred in the northwestern
part of the UGoT in November, and there was no hypoxia from December to April.
Again hypoxia appeared in June between river mouths of Chaopraya and Bangpakong.
Hypoxia appeared in the northeastern part of the UGoT in early rainy season and
moved to westward with seasons. We also developed a coupled physical-ecosystem
model to understand spatial and temporal variation in hypoxia in the UGoT. We
examined generation mechanism of hypoxia in the UGoT and influence of river
discharge change to the magnitude of hypoxia.
Keywords: Hypoxia, Upper Gulf of Thailand, Lower Trophic ecosystem model
16
Title: On Ocean Circulation, Ecosystem and Hypoxia along the coastal transition zone
off Hong Kong (OCEAN_HK)
Jianping Gan
Department of Ocean Science, Hong Kong University of Science and Technology,
Hong Kong
Abstract:
The coastal waters around Hong Kong are affected by persistent and increasing
eutrophication. This deteriorating situation may increase the frequency of HABs,
expand the area of hypoxic zones and lead to other ecosystem disruptions and worse of
all, offset the environmental improvements achieved through the costly Harbour Area
Treatment Scheme over the last decade. Eutrophication/hypoxia in Hong Kong waters
is primarily caused by the ecosystem’s responses to the increasing nutrient discharge
from the Pearl River and local sewage effluent. Highly variable oceanic currents
transport the nutrients in the interactive river-estuary-shelf (RES) waters around Hong
Kong, which undergo complex coupled physical-biogeochemical processes and
modulate eutrophication/hypoxia. To date, these key processes have not been
investigated in a comprehensive manner in the RES waters, and they remain largely
unresolved in similar ecosystems elsewhere in the world. Understanding the full
spectrum of coupled physical and biogeochemical processes in eutrophication is crucial
to predicting and mitigating the impacts of eutrophication, and it remains a huge
scientific challenge regionally and globally. The grand OCEAN_HK project
(https://ocean.ust.hk/) aims to determine sources and sinks of nutrients, their
biogeochemical controls, ecosystem dynamics, and physical controls on the
eutrophication/hypoxia in the RES waters. By conducting an interdisciplinary study,
we investigate the coupled physical-biological-chemical processes in this interactive
RES system, and diagnose the eutrophication/hypoxia in the study region. We
conducted interdisciplinary mapping and time-series measurements, and based on them,
developed a novel coupled physical-biogeochemical modelling system. This
presentation summarized the research findings in chemical-biological-physical aspects
on the eutrophication and hypoxia studies in the coastal transition off HK waters.
17
Title: The eutrophication states and nutrient-phytoplankton dynamics of eutrophied
tropical embayment of Jakarta Bay, Indonesia: temporal dynamics from 2001 to 2017
Ario Damar1,2, Achmad Fahrudin1,2, Karl-J. Hesse3, Franciscus Colijn4 and
Yonvitner2
1Center for Coastal and Marine Resources Studies – Bogor Agricultural University,
Indonesia2Department of MSP, FPIK, Bogor Agricultural University, Indonesia 3Forschungs-und Technologie Zentrum – Westkueste – University of Kiel, Germany 4Institute for Coastal Research, Centre for Material and Coastal Research, Helmholtz-
Zentrum Geestacht, Max-Planck-Strasse 1, 21502 Geestacht, Germany
Abstract: Eutrophication states of the most eutrophied tropical embayment in
Indonesian waters was studied over the period of 2001-2017 in Jakarta Bay. There was
a clear gradient of dissolved inorganic nutrient concentration, showing very high values
in the river mouths and steeply decrease down the bay. This is followed by a steep
gradient of Chl-a concentration, showing high phytoplankton biomass in the river
mouths (29.2 µg Chl-a l-1) and then decrease 2 folds in the near coastal waters (14.8
µg Chl-a l-1) for then decreased 4 folds in the middle (6.3 µg Chl-a l-1) and finally 14
folds in the outer part of the bay (2.1 µg Chl-a l-1). There is no significant change in
nutrient concentration (except nitrogen), phytoplankton biomass and thus
eutrophication level during the last 16 years period (between 2001 to 2017), showing
relatively stable but high nutrient pollution level in Jakarta Bay. Eutrophication level
analysis resulted high level of eutrophication in the bay. Hyper-eutrophic level is
always pronounced along the near-shore part of the bay, for then decreases to eutrophic
level in the middle of the bay and mesotrophic class in the outer part of the bay. Algae
bloom and hypoxia becomes a regular phenomenon which leads to mass mortality of
fish in this bay.
Keywords: eutrophication, nutrient, phytoplankton, chlorophyll-a, estuarine
18
Title: The environmental study to understand the hypoxia behavior in Jakarta Bay
Suhendar I Sachoemar1, Yuichi Hayami2, Akihiko Morimoto3, Agus Sudaryanto1,
M. Saleh Nugrahadi4, Endro Soeyanto1, M.Ilyas1 and Ratu Siti Aliah1
1. Agency for the Assessment and Application of Technology (BPPT), Jakarta
Indonesia.
2. Saga University, Japan. Institute of Lowland and Marine Research, Saga
University. Saga, Japan
3. Center for Marine Environmental Studies, Ehime University.
Matsuyama, Japan .
4. Coordinating Ministry for Marine Affair. Jakarta. Indonesia.
Abstract:
Jakarta Bay is a semi enclosed estuary located in the northern coastal area of
Jakarta which is surrounded by 13 rivers from 3 provinces (Province Jakarta, West
Java and Banten) which empties into the Jakarta Bay. As a consequence, Jakarta Bay
has become a place for the emergence of various pollutants carried by 13 rivers from
the three provinces in the form of household organic waste and industrial waste. Often
the occurrence of mass deaths in fish in Jakarta Bay is thought to be due to the
accumulation of the anthropogenic and industrial waste in the coastal areas of Jakarta
Bay which can form dead zones in the form of hypoxia in the bottom layers with low
DO concentrations. Until now, the actual cause of the frequent occurrence of mass
death in fish in the Jakarta Bay is unknown, whether due to the direct pollution or
upwelling from hypoxia. To find out and understand the problem, a study of hypoxia
in Jakarta Bay is needed.
19
Title: Behavior and residence time of river waters in Jakarta Bay
Akihiko Morimoto1, Endro Soeyanto2
1Center for Marine Environmental Studies, Ehime University, Japan2Agency for Assessment and Application Technology (BPPT), Indonesia
Abstract: The present study using a 3D–numerical modelling technique to predict an
overview of temperature, salinity, current velocity distribution in Jakarta Bay, Indonesia in
the period year 2016. Furthermore, this ocean model applies to overview the seasonal
variation of these parameters and behavior of water age in the bay. Seasonally, the surface
current fields in Jakarta Bay controlled the behavior and residence time of river waters in
Jakarta Bay. Dominant flows of the river mouths that flow to the bay are from eastern side
of the Jakarta Bay. Citarum river gives only highest of contribution rate and shortest age
water in transition rainy to dry season (May 2016).
Keywords: Jakarta Bay, 3D numerical modeling, seasonal variation, residence time of river
water
20
Title: Long-term change in the state of water pollution in Tokyo Bay: Tokyo Bay, trend
analysis, COD, nutrients and hypoxia
Haruo Ando1, Nobuhisa Kashiwagi2, Yuuichi Ishii1, Hideaki Maki3
1. Tokyo Metropolitan Research Institute for Environmental Protection, Tokyo, Japan
2. The Institute of Statistical Mathematics, Tokyo, Japan
3. National Institute for Environmental Studies, Ibaraki, Japan
Abstract:
Tokyo Bay is one of the major coastal seas in Japan. About 31 million people live in
the drainage basin accounting for 24% of the total population in Japan. The basin
includes the Tokyo metropolitan area, which is the political and economic center of
Japan.
During the period of high economic growth that began in the 1950s, the water quality
of Tokyo Bay deteriorated rapidly. As a countermeasure to address this problem, in
1979 the Total Pollutant Load Control System was introduced to reduce the total
amount of COD flowing into Tokyo Bay. In 2001 the system was expanded to include
total nitrogen and total phosphorus as causative substances for eutrophication.
Consequently the amount of those pollutants produced in the drainage basin was
estimated to be greatly reduced.
We have studied the long-term trend of water quality in Tokyo Bay to evaluate the
effects of water pollution prevention measures. In Tokyo Bay, water quality has been
measured by the relevant local governments every month at scores of monitoring points
for administrative purposes since 1970s. We used a seasonal adjustment method to
analyze these data and estimated the trend of water quality.
The result shows that overall the water quality of Tokyo Bay has been improving,
but the degree of improvement is different depending on the sea areas. In the eastern
side of the bay, the nutrient concentration has decreased considerably. However, in the
western side especially around Tokyo, even today the level of nutrient concentration is
still high enough for an outbreak of red tide. Because major inflowing rivers and most
large-scale sewage treatment plants are located around this area. As a consequence,
hypoxia and anoxia frequently occur in the bottom water during the warm season in
this area.
21
Title: Tempo-spatial variations of hypoxia water and nutrient conditions, and emerging
problems in Osaka Bay, Japan
Satoshi Akiyama1, Masaki Nakajima2
1. Marine Fisheries Research Center, Research Institute of Environment, Agriculture
and Fisheries, Osaka Prefecture, Misaki, Osaka, Japan
2. Research Institute of Environment, Agriculture and Fisheries, Osaka Prefecture,
Habikino, Osaka, Japan
Abstract:
Osaka Bay is located in eastern Seto Inland Sea, Japan, and more than 17 million
people lives in the catchment area. Over the past 60 years, the bay has undergone
various artificial and natural changes, such as coastal reclamation, water pollution and
eutrophication accelerated with industrial development and population growth, and the
following total pollutant load control and global/regional warming.
In this presentation, we demonstrate transition of occurrence of hypoxia water mass
and nutrient conditions in Osaka Bay, using results of water quality monitoring since
1972. From 1970s to 1990s, the area of hypoxia water mass had been reduced in
summer, and then has continued approximately constantly. Dissolved nutrient
concentration reached peaks from 1970s to 1980s, and have steadily decreased since
then. DIN/DIP ratio was temporarily increased in 1980s, with sharp decrease in DIP,
and began to show downward trends in 1990s. And, since 2000s, the number of
monitoring station where DIN/DIP ratio is falling below the Redfield ratio is increasing.
Like this, in Osaka Bay, trophic and dissolved oxygen conditions have drastically
changed. And, in recent years, shortages and uneven distribution of nutrients have been
new problems. Since they should have been associated with lower biological
productivity and less fish catch, marine environmental conservation considering the
bioproductivity would be required for the future.
22
Title: Oxygen consumption rate in the Mikawa Bay using an optical oxygen sensor
Chiho Sukigara1, Yoshihisa Mino2, Akira Yasuda3, Akihiko Morimoto4, Joji
Ishizaka2
1. Center for Marine Research and Operation, Tokyo University of Marine Science
and Technology, Tokyo, Japan
2. Institute for Space-Earth Environmental Research, Nagoya University, Nagoya,
Japan
3. Tokai Marinos Tech, Tokoname, Japan
4. Graduate School of Science and Engineering, Ehime, University, Matsuyama,
Japan
Abstract:
Oxygen consumption rate (OCR) of bottom waters at 4 stations from the inner part
to the mouth of the Mikawa Bay during May to August 2014 was estimated from dark
bottle incubations using an optical oxygen sensor (FirestingO2, Pyroscience). An error
of oxygen measurement by this sensor (3.26 mol kg-1) was sufficiently low to
evaluate the OCR in the Mikawa Bay. Larger OCR was found in the inner most point
than others all the time, with the maximum of 38.3 mol kg-1 d-1 in August 24th.
Among six observations, low-oxygen water masses (<20 % of oxygen saturation)
appeared at the bottom water from the inner to the middle part of the bay in June 24th,
July 31st, and August 24th when larger density differences were found in which
atmospheric O2 exchange was inhibited. Severe hypoxia would be formed and
maintained by a large OCR and a strong and stable stratification.
23
Title: Hypoxic water mass in Ariake Sea, Japan -mechanisms of multi-time scale
variations-
Yuichi Hayami1
1. Faculty of Agriculture, Saga University, Saga, Japan
Abstract:
Ariake Sea is a semi-enclosed coastal water located in Kyushu island, southwestern
Japan. The Chikugo River which is the biggest river in Kyushu flows into the inner part
of this bay. Recently, serious hypoxia occurred every summer and generated massive
kill of bivalves in this bay. The formation of hypoxia was triggered by the enhancement
of stratification of water column. The freshet of river was the most important factor
which enhanced stratification. The other factor which enhanced stratification was the
intrusion of high density water from offshore during neap tide. Therefore, there is a
spring-neap cycle variation in hypoxia. The interannual variation of hypoxia was
generated by the river discharge. When the river discharge was large, the hypoxia
became serious and continued longer. More longer time scale, the variation of hypoxia
in Ariake Sea was generated by the organic matter production in the bay and 18.6-year
lunar nodal variation. When the M2 tidal range became smaller due to the lunar nodal
variation, stratification became stronger and hypoxia became more serious. We
estimated the potential for hypoxia removing the effects of the variation in stratification.
The potential of hypoxia increased from 1972s to early 90s. The Chemical Oxygen
Demand which is an index of organic matter concentration increased in the same period.
There was a high negative correlation between the potential of hypoxia and COD. The
results of the box model analysis indicated that the COD increase was generated by the
internal production. In this period, the bivalve population in the bay largely decreased.
Therefore, the decrease of the predation by bivalves enhanced the production of
phytoplankton in the bay. Except for them, the construction of the Isahaya Sea dike
enhanced the hypoxia.
24
Title: Disappearance of Hypoxia in Dokai Bay, Japan
Tetsuo Yanagi1
1. Professor of Emeritus, Kyushu University
Abstract:
Dokai Bay suffered from severe hypoxia during 1960-2000 but it disappeared in
2010 as shown in Fig.1. This is mainly due to the strict application of the total
pollution load reduction law from land. TP load was decreased by about 80 % and
TN load by about 60 % from 1998 to 2010.
Other trials such as dredging, bio-remediation, citizen participation and so on are
introduced in this presentation.
Fig.1 Year-to-year variation in Hypoxia in Dpkai Bay
Station
DO (mg L-1)
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25
Title: Enhancing water exchange and suppressing the effects of anoxic water in an inner bay by
placement of water flow pipes through tsunami protection breakwaters
Keyword: tsunami protection breakwater, environmental operation, anoxic water, water exchange,
Ofunato Bay
Osamu Shimozawa1, Toshiyuki Takao2, Kazuo Murakami3, Yoshiyuki Nakamura4
Ikuo Abe5, Tomonari Okada6, Toshinori Ogasawara7, Hidenori Shibaki8
1. Tohoku Regional Bureau Ministry of Land, Transport and Tourism, Kamaishi, Iwate, Japan
2. Waterfront Vitalization and Environment Research Foundation, Minato-ku, Tokyo, Japan
3. Japan Sediments Management Association, Chuo-ku, Tokyo, Japan
4. Yokohama National University, Yokohama, Kanagawa, Japan
5. Tokoha University, Shizuoka, Shizuoka, Japan
6. National Institute for Land and Infrastructure Management, Yokosuka, Kanagawa, Japan
7. Iwate University, Morioka, Iwate, Japan
8. ECOH Corporation, Taito-ku, Tokyo, Japan
Abstract:
Before the unexpected massive tsunami generated by the 2011 Tohoku Earthquake in March
2011, large-scale anoxic water masses were formed in the middle to lower layers in Ofunato bay
from summer to autumn every year. The tsunami protection breakwaters including their mounds at
the mouth of the bay were almost collapsed by the tsunami disaster. Post-disaster field
measurement data showed that the dissolved oxygen concentration in the bay was kept high even
in summer and autumn seasons. The field observation and numerical analysis revealed that the
major reason for the decline in the anoxia formation was attributed to enhanced intrusions of low
temperature, high dissolved oxygen water mass into the lower part of the bay, which was associated
with elevation of the internal density interface off the coast of Ofunato bay. As a result, effective
water exchange at the bottom of the bay was promoted to reduce anoxia development.
Therefore, eighteen water flow pipes (diameter 3.5 m) were installed in lower part of the mounds
(water depth 31 m) for the reconstruction of tsunami protection breakwaters. Observation data of
dissolved oxygen concentration after the construction of the mounds showed higher values than
that before the tsunami. At the same time, observation data of the current in those pipes showed an
oscillation with semi-diurnal cycle when the depth of the internal density interface was higher than
those pipes, and a constant outflow when the depth of the interface was lower than the pipes. The
constant outflow was induced by the density difference between warmer water mass of the outer
bay and the lower temperature water mass, which was intruded from outer bay to inner bay during
the oscillation period. Numerical modeling analysis revealed that the discharging mechanism of the
lower layer water through the pipes effectively suppressed the anoxic formation.
26
Title: Decadal and centennial oscillation in Japanese sardine abundance during the last
2,900 years
Michinobu Kuwae1
1. Center for Marine Environmental Studies, Ehime University
Abstract
How changes in nutrient conditions in the Seto Inland Sea influence fish abundance is
recent active research and is important for fishery resource prediction. However, fish
abundance does not necessarily respond to the nutrient conditions in the inland sea. There
may be some species depending on open ocean environments. Here I address long-term
variability in sardine and anchovy abundance using fossil fish scales in Beppu Bay
sediments and their responses to open ocean environments and climate variability in the
Pacific. On the basis of this information, I address whether these species responded to
nutrient conditions, in particular in the western Seto Inland Sea for the past millennia.
For the former topic, I discuss whether Japanese ‘sardine regime’ comes back in the
next decades based on our paleo-fish-productivity data reconstructed from Beppu Bay
sediments and published paleoclimate data. We found that sardine population showed
centennial-scale variability in association with reconstructed PDO indices, likely
responding to open ocean climate variability in the Pacific. If the centennial climate
forcing on Japanese sardine recruitments are still dominant, Japanese sardine regime does
not necessarily come back in the next decades because of potential entering into the
negative phase of the centennial variations in sardine abundance.
For the latter topic, I address responses of these species to nutrient conditions in the
western Seto Inland sea for the past millennia to test if these species have been influenced
by nutrient environments in the inland sea. We found that there is no evidence supporting
this hypothesis, rather showing negative relationship between fish and phyto-/zoo-
plankton productivity during several periods. Anchovy and sardine in the Seto Inland Sea
might migrate from slope and offshore environments in the Pacific; their abundance might
result from temperature or nutrients and recruitments of the populations in these regions.
27
Title: Long-term variation of nutrient concentration in the Western Seto Inland Sea
Naoki Yoshie1, Sohei Ogawa1, and Hidejiro Ohnishi1
1. Center for Marine Environmental Studies, Ehime University, Matsuyama, Japan
Abstract:
The nutrient concentration around the Sada-Misaki strait is a representative nutrient
concentration in the Western Seto Inland Sea because of the huge horizontal and
vertical mixing around the narrow strait with the strong tidal current. We have
observed the long-term variation of the nutrient concentration by daily nutrient
monitoring from 2004 at cape Sada-Misaki where is located at the tip of the Sada-
Misaki peninsula which is the longest thin peninsula in Japan. We investigated
seasonal and interannual variations of the nutrient concentration and mechanisms of
these variations concerning with nutrient supplies from terrestrial and offshore regions.
The seasonal variations of nitrate and phosphate were typical variations with the
maximum in the winter and the minimum in the summer, while the variation of
silicate had second maximum in the summer due to the high-silicate water discharge
from the terrestrial region during the rainy season. The interannual variations of
nitrate and phosphate were affected by the bottom intrusion of the offshore water
originated from Kuroshio subsurface water in the summer. On the other hand, the
variation of silicate was affected by the river discharge in the northern part of Kyushu
during the rainy season. There was no clear decreasing trend of the nutrient
concentration observed in the Eastern Seto Inland Sea, where the water depth is
shallower and the nutrient supply from the terrestrial region is larger than those in the
Western Seto Inland Sea. As nitrogen is limiting nutrient of primary productivity in
this region, the interannual variation of the productivity in this region might be
controlled by the nutrient supply from the Kuroshio subsurface water in the summer.
28
Title: Human-induced marine ecological degradation: historical ecology and the
Anthropocene
Moriaki Yasuhara1
1. School of Biological Sciences and Swire Institute of Marine Science, The University
of Hong Kong, Kadoorie Biological Sciences Building, Pokfulam Road, Hong Kong
SAR, China
Abstract:
We analyzed published downcore microfossil records from 150 studies and
reinterpreted them from an ecological degradation perspective to address the following
critical but still imperfectly answered questions related to the Anthropocene: (1) How
is the timing of human-induced degradation of marine ecosystems different among
regions? (2) What are the dominant causes of human-induced marine ecological
degradation? (3) How can we better document natural variability and thereby avoid the
problem of shifting baselines of comparison as degradation progresses over time? The
results indicated that: (1) ecological degradation in marine systems began significantly
earlier in Europe and North America (~1800s) compared with Asia (post-1900) due to
earlier industrialization in European and North American countries, (2) ecological
degradation accelerated globally in the late 20th century due to post-World War II
economic growth, (3) recovery from the degraded state in late 20th century following
various restoration efforts and environmental regulations occurred only in limited
localities. Although complex in detail, typical signs of ecological degradation were
diversity decline, dramatic changes in total abundance, decrease in benthic and/or
sensitive species, and increase in planktic, resistant, toxic, and/or introduced species.
The predominant cause of degradation detected in these microfossil records was
nutrient enrichment and the resulting symptoms of eutrophication, including hypoxia.
Other causes also played considerable roles in some areas, including severe metal
pollution around mining sites, water acidification by acidic wastewater, and salinity
changes from construction of causeways, dikes, and channels, deforestation, and land
clearance. Microfossils enable reconstruction of the ecological history of the past 10^2–
10^3 years or even more, and, in conjunction with statistical modeling approaches using
independent proxy records of climate and human-induced environmental changes,
future research will enable workers to better address Shifting Baseline Syndrome and
separate anthropogenic impacts from background natural variability.
29
Title: A challenge on measuring photosynthetic oxygen evolution by optical sensors in
the Tokyo Bay, off Haneda
Naho Miyazaki1, Chiho Sukigara2, Karla Loza Choque3, Issei Hamana3, Yoshihisa
Mino4, Akihiko Morimoto5
1Department of Ocean Sciences, Tokyo University of Marine Science and Technology,
Japan
2Center for Marine Research and Operations, Tokyo University of Marine Science and
Technology, Japan
3School of Marine Resources and Environment, Tokyo University of Marine Science
and Technology, Japan
4Institute for Space-Earth Environmental Research, Nagoya University, Japan5Center for Marine Environmental Studies, Ehime University, Japan
Abstract: The inner part of Tokyo Bay forms shallow and vast estuaries is known as one of the
enclosed coastal seas in the world. Coastal estuaries are not only places with high productivity area,
but high biodiversity is providing many useful ecosystem services for human. This result
preliminary reports that oxygen gross primary productivity (GPP) estimation in Tokyo Bay off
Haneda during 2018-19. Primary productivity as three methods were measured by the simulated in
situ incubation under different light intensities about for five hours; high precision Winkler titrations
(Grasshoff, 1983) and net primary production (NPP) from 13C uptake rates (Hama et al., 1983) with
in situ quantification of oxygen generation rate in the same vials using fiber optic oxygen sensors
(FireStingO2, Pyro Science GmbH, Aachen, Germany). This fiber optic O2 sensors were glued to
the interior of the glass vials, and the sensor spots The FireSting oxygen meters excites the indicators
with a 620 nm LED and measures the luminescent lifetime of the indicators using the phase
modulation method (Holst et al. 1995). Two approaches of oxygen generation as the optical sensor
and precise titrations showed good agreement (r2=0.96, p<0.01), suggested that GPP can be
monitored using the optical sensor that easy handle with immediate results. The minimum value of
GPP was 1.0 µmol O2 kg-1 h-1 in December, and the maximum value was 42.6 µmol O2 kg-1 h-1 in
August by the Winkler method. The maximum GPP under light saturation conditions were ranging
between 0.36 and 1.41 µmol O2 µg Chl. a -1 h-1 in this study, almost same as four decades ago (0.05-
2.5 µmol O2 µg Chl.a -1 h-1, Yamaguchi et al., 1988).
We plan to estimate particulate organic carbon (13C-POC) as NPP and then compare to GPP
measurement, to facilitate for simplified productivity measurement methods in future.
Keywords: Primary productivity, Tokyo Bay, Oxygen generation, Carbon uptake.
30
P-01
Title: The river discharge can change the peak and its occurrence time of the
Chlorophyll-a in a semi-enclosed sea
Xiaokun Ding1
1. Key Laboratory of Marine Environment and Ecology, Ocean University of China,
Ministry of Education of China, Qingdao,
Abstract:
The peak and its occurrence time of the Chlorophyll-a concentration (Chl-a) are not
often fixed in the coastal area, due to the dual influence of human activities and natural
factors. For example, the seasonal variation of the Chl-a may show two peaks in spring
and autumn or one peak in summer, directly affected by the nutrients supply, convective
mixing for phytoplankton, etc. In the Bohai Sea (BHS), which is a typical semi-
enclosed sea in the Northwest Pacific, the seasonal pattern of sea surface Chl-a has not
been yet unsterdood in recent decades. The paper specifically introduces the change in
seasonal pattern of the Chl-a in the BHS, using the previous in-situ data and satellite-
derived data. The results show that the seasonal pattern of the Chl-a has gradually
changed from two peaks in spring and autumn to high value of the Chl-a in spring and
summer in recent decades. The shift year is around 2002. Moreover, the annual range
of seasonal variation in the Chl-a increased significantly with a higher value (~2.2
mg∙m-3) of average after 2002 than before (~0.4 mg∙m-3). A large amount of nutrients
loads in summer due to the Water-Sediment Regulation Scheme (WSRS) play a vital
role in the change in seasonal pattern of the Chl-a while other factors have a little
influence. The model results show that the WSRS can generally increase the Chl-a and
primary productivity over the whole central area by 0.04 mg Chl-a∙m-3 and 3.19 mg
C∙m-2∙d-1 respectively per 108 m3 fresh water into the sea. The above change maybe also
has a drastic effect on the zooplankton and aquaculture by changing the feed supply
and water quality. This work helps clarify the seasonal pattern of the Chl-a in a typical
semi-enclosed sea and maybe promotes the study on the impact of human activities on
the marine ecosystem through showing a new case.
Keywords: Chlorophyll-a; Seasonal pattern; Change; River discharge; Bohai Sea
31
P-10
Title: Annual Cycles and Budgets of Nutrients in the Yellow Sea: a model study
Hao Jiang1, Liang Zhao1, Yihan Wu1
1. College of Marine and Environmental Sciences, Tianjin University of Science and
Technology, 29, 13th. Avenue, Tianjin Economic and Technological Development
Area, Tianjin, P.R. China.
Abstract:
To study the annual cycles and budgets of both dissolved inorganic nitrogen (DIN)
and particulate organic nitrogen (PON) in the Yellow Sea, a three-dimensional coupled
biophysical model (ECSECOM) was established. We simulated the DIN and PON
cycles in the Yellow Sea, calculated the annual budgets of nitrogen and analyzed the
spatial distributions and seasonal variations of each sources and sinks of DIN and PON.
The results indicate that (1) The DIN concentration decreases through spring and
summer due to the spring blooms and reaches the lowest value in June-August, then
increases greatly in autumn. The concentration of PON is low in winter and spring, and
increases in summer and autumn following the growth of chlorophyll-a and peaks in
September. (2) Regarding the budgets of DIN, primary production and respiration of
phytoplankton are the most important sink and source of DIN. The remineralization of
the detritus pool compensates 21.5% of the consumption of DIN by the primary
production process, while external input of DIN accounts for 18.1%. The external
inputs of DIN are dominated by sediment-water interface exchange in mud areas in the
central part of the Yellow Sea, the eastern part of the Bohai Strait and the center of the
North Yellow Sea. The input of DIN from atmospheric deposition to the Yellow Sea is
comprehensive, and the area affected by the bottom interface release and river loading
is regional. (3) The major source of PON is mortality release of phytoplankton. The
exchange of sediment-seawater interface of PON show a net sedimentation. The
transformation rate between DIN and PON is also calculated. There are 76.5% of PON
converting to DIN, the most of the rest PON deposit to the sediment. The transformation
rate from DIN to PON is 30.0%.
32
P-10
Title: Estimate of environmental capacity of dissolved inorganic nitrogen in the
Xiangshan Bay
Jun-Yong ZHENG 1, Xin-Yan MAO 1, Xiao-Xuan SHENG 1, Jian-An SUN 2, Wen-Sheng
JIANG 3
1. College of Oceanic and Atmospheric Sciences, Ocean University of China, Qingdao
266100, China;
2. Ningbo Scientific Research and Design Institute of Environmental Protection,
Ningbo 315012, China;
3. College of Environmental Science and Engineering, Ocean University of China,
Qingdao 266100, China
Abstract: A three-dimensional water quality model in the Xiangshan Bay was
established based on ROMS (Regional Ocean Model System) to simulate the
distribution of dissolved inorganic nitrogen (DIN) in the Xiangshan Bay, including 10
land-based discharge sources. In the condition of class I water quality standard, the
discharge optimization method was applied to calculate the environmental capacity (EC)
of DIN with the minimum DIN discharge concentration (Rmin) getting larger. The results
show that the EC of DIN in the Xiangshan Bay is 167.16~274.17 t/a. The capacity will
decrease when Rmin gets larger, which means more discharge flux of DIN needed to be
cut down. According to the reduction priority, the ten discharge sources can be divided
into four levels, which mainly depends on the water half-exchange time and annual
DIN discharge flux.
33
P-10
Title: Study on the Response Mechanism of Primary Production in the East China Sea
to the Change of Nutrient Inputs from the Yangtze River
Qian Leng1, Jie Shi1, Xinyu Guo2
1. Key Laboratory of Marine Environmental and Ecology, Ocean University of China,
238 Songling Road, Qingdao, Shandong Province, China, 2 Center for Marine
Environmental Studies, Ehime University, Bunkyo-cho 2-5, Matsuyama, Ehime, 790-
8577, Japan
Abstract:
Using a three-dimensional coupled biophysical model, we simulated the responses of
primary production in the East China Sea (ECS) to long-term changes in nutrient
transport from the Yangtze River during 1960–2005. Nutrient transport was affected by
combined effect of river discharge and nutrient concentration. Increasing river
discharge accompanied with increasing nutrient transport raised nutrient concentration
except phosphate in most parts of ECS. Increasing part was quickly consumed through
primary production for phosphate is a candidate limiting factor. Increasing river
discharge also caused dramatic changes in physical situation in the estuary and further
strongly affected the ecological processes. Due to increased use of chemical fertilizer
and construction of water conservancy projects, increasing nitrate and phosphate
concentrations in the river primarily led to increases in nitrate, phosphate, and primary
production in the ECS, whereas decreases in silicate concentration in the river led to
lower silicate concentrations in the ECS, indicating that silicate is not a limiting nutrient
for photosynthesis. Increasing N/P and N/Si ratios in the Yangtze River could lead to
main algae changing from diatom to dinoflagellate. As flooding events and
anthropogenic activities will increase in the future, it is significant to find out the
response mechanism of primary production in the ECS from nutrient transport from
Yangtze River.
34
P-10
Title: A simulation of the seasonal variation of decabromodiphenyl ether in a bay
adjacent to the Yellow Sea
Aobo WANG1, Xinyu GUO2, Jie SHI1, 3, Chongxin LUO1, Huiwang GAO1, 3
1. Key laboratory of Marine Environment and Ecology, Ocean University of China,
Ministry of Education, Qingdao, China
2. Center for Marine Environmental Studies, Ehime University, Matsuyama, Japan
3. Laboratory for Marine Ecology and Environmental Sciences, Qingdao National
Laboratory for Marine Science and Technology, Qingdao, China
Abstract:
A three-dimensional transport-ecosystem-POP coupled model is configured to
simulate the seasonal variation and budget of decabromodiphenyl ether (BDE-209) in
a semi-enclosed bay adjacent to the Yellow Sea. The model includes five types of
BDE-209 (gaseous, dissolved, phytoplankton-bound, detritus-bound, and suspended
particulate matter (SPM)-bound) and related physical and biogeochemical processes,
such as advection and diffusion due to seawater motion, input from rivers, air-sea
exchange, decomposition of dissolved BDE-209, uptake and depuration between
dissolved and phytoplankton-bound BDE-209, mortality of phytoplankton-bound
BDE-209, remineralization and sinking of detritus-bound BDE-209, and sinking of
SPM-bound BDE-209. Model results show that the dissolved and particulate BDE-
209 in the bay are higher in the nearshore area than in offshore area and are higher in
summer than in other seasons; these results are consistent with field data. SPM-bound
BDE-209 is dominant among the five types due to its large supplying from rivers.
Dissolved BDE-209 concentrations are around 5-fold that of phytoplankton-bound
BDE-209, which depends on uptake and depuration rate constants between dissolved
and phytoplankton-bound BDE-209 and biomass of phytoplankton. Evaluation of
mass balance indicates that the input from rivers is major source of BDE-209, while
the exchange with the Yellow Sea is major sink. Sensitivity experiments demonstrate
that the input of BDE-209 from rivers plays the most significant role in the seasonal
variation of dissolved and particulate BDE-209 concentrations, and the change in
water temperature is a secondary factor.
Reference:
Wang, A., Guo, X., Shi, J., Luo, C., Gao, H., 2019. A simulation of the seasonal
variation of decabromodiphenyl ether in a bay adjacent to the Yellow Sea. Science of
the Total Environment 664, 522–535. https://doi.org/10.1016/j.scitotenv.2019.01.385
35
P-10
Title: Organic Carbon Distribution and Budget in the Changjiang Diluted Plume based
on Chemical analysis and Numerical Model
Xiaolu Wang1; Ying Wu1; Hui Wu1; Lijun Qi1; Jinlong Dai1; Zhaoru Zhang2; Meng Zhou2
1. State Key Laboratory of Estuarine and Coastal Research, East China Normal University,
Shanghai 200241, China
2. Institute of Oceanology, Shanghai Jiao Tong University, Shanghai 200240, China
Abstract:
River plume carries lots of materials to adjacent sea, interacting with local ecological
environment and has great influence on carbon cycling. However it is difficult to
quantify organic carbon (OC) budget in such dynamic region while there are many
studies about descriptive of their distribution and behavior only. In this study, based on
a three-dimensional numerical model combined with in situ chemical analysis, we
characterized the distribution and budgets of OC along the Changjiang Diluted Water
especially the residence time (RT) of water mass and phytoplankton contribution to OC
were quantitative estimated. Integrated all physical and chemical parameters, very
different two typical groups (estuarine region and coastal region) were identified by the
principal component analysis (PCA). In estuarine region, the average RT was 4.9 days
while it was 39 days in coastal region, and the longer RT allows phytoplankton
blooming during the spread of the Changjiang Diluted Plume in the offshore. We found,
in coastal surface layer, about 17.4% (±10.2%) of DOC and 74.8% (±17.4%) of POC
was derived from phytoplankton in situ production while it was only 2.9% (±6.6%) of
DOC and 12.1% (±9.8%) of POC in estuarine region and about 30.2% contribution of
OC was from the Changjiang. This study first quantitatively estimated the influence of
Changjiang plume on carbon cycling of the Eeast China Sea and will shed light on the
biogeochemistry of terrestrial delivery of OC in the dynamic coast.
36
P-10
Title: The role of submesoscale advections on vertical heat and nutrient transports in
the Southern East China Sea
Jiliang Xuan1, Qicheng Meng1, Feng Zhou1, Daji Huang1
1. State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of
Oceanography, Ministry of Natural Resources, Hangzhou, China
Abstract:
Horizontal resolutions of regional ocean models are often not sufficient to resolve
submesoscale vertical advection (SVA) in continental shelf seas. In this study, we
investigate the role of SVA on vertical heat and nutrient transports through two similar
models in the Southern East China Sea with different horizontal resolutions. (1) The
SVA increases downward heat transport in early autumn. An internal warming process
is significant in both the observations and the high-resolution model (HRM) but is
absent in the high-resolution model (LRM). Combined with the observations, we found
that the internal warming, which occurred in the barrier layer of the water column in
early autumn, is accompanied by submesoscale oscillations of isothermals in the HRM.
SVA increases the total vertical advection by up to an order of magnitude in the HRM
compared with the LRM and dominates the internal warming process. (2) The SVA
increases upward nutrient transport in the whole year, which contributes to the
Phytoplankton Production mainly in summer. Weak SVA with great positive
contribution to the Phytoplankton Production in summer is mainly due to the strong
stratification and intensive Photosynthetically Active Radiation. In such circumstance,
SVA provides a significant vertical nutrient supplement pathway particularly on the
middle shelf. Intensive Photosynthetically Active Radiation facilitates the
phytoplankton growth by making full use of the replenished nutrient.
37
P-10
Title: Upstream propagation of a bottom-advected plume and its influencing factors
Xiaojie Yu1
1. College of Environmental Science and Engineering, Ocean University of China,
Songling Road, Qingdao, China.
Abstract:
Several summer hydrographic data during sharp variation of river discharge in the
Yellow River revealed that the Yellow River plume propagated upstream under low
river discharge, in a direction opposite to that of a Kelvin wave, but turned downstream
after river discharge increased. A numerical model for the Bohai Sea reproduced the
upstream propagation of the Yellow River plume under low river discharge, as well as
the alternation to downstream direction under high river discharge. Through numerical
experiments, the upstream extension of the Yellow River plume is found to feature
significant spring and neap variation. During spring tide, the Yellow River plume is
bottom-advected plume and extends upstream, while during neap tide, the plume
becomes surface-advected and turns downstream. The mechanism driving the upstream
propagation of the bottom-advected plume in spring tide is the Euler tidal residual
current in the bottom boundary layer, which flows upstream-ward near the Yellow River
mouth. The surface-advected plume in neap tide detaches from the bottom layer and is
deflected downstream by the Coriolis force. Further analysis indicates that the vertical
structure of the plume determines the propagation direction of the plume. After river
discharge increases, the Yellow River plume becomes surface-advected in spring tide
and consequently turns downstream. The momentum balance of the plume transforms
from advection dominated in low river discharge to Coriolis force dominated in high
river discharge. Besides, summer wind has little influence on the upstream extension of
the Yellow River plume under low river discharge in spring tide.
38
P-10
Title: Effects of climate change and human activities on the dynamics of fisheries
community and succession of dominant species in Zhoushan archipelago Seas
Yongjiu Xu1
1. School of Fisheries, Zhejiang Ocean University, China
Abstract:
The effect of climate change, fishing activity, stock enhancement and fisheries
management policy on dynamic of fisheries community structure were rarely evaluated
in the Zhoushan archipelago areas. According to the fisheries survey between 2015 to
2018, which corresponded to the critical periods of those activities above, we quantified
the effect of fishing activity on the dynamic of dominant fish, the effect of fisheries
recovery management, and the climate change on the critical stage of fisheries
recruitment. The results indicated that the climate change and human activities have
significant influence on the dynamics of fisheries community. The comparison to the
previous datasets indicated that there is a significantly increasing trend of the
abundance of dominant species during recent decades. Human related activities
explained more than 50% of the long-term dynamic of fisheries community, rather than
the climate change, however, for their seasonal dynamic, climate change played an
more important role. The long term influence were more reflected on the size of
dominant species, while, the short-term influence were reflected on their abundance.
The fisheries management policy benefited the long-term dynamics of fisheries size
community, through increasing the size of most dominant species. The climate change
in spring strongly affected the subsequent recruitment of dominant species. These
results probably reflected different fisheries response strategy, and fisheries
management should consider different responses.
39
P-10
